atw 2018-04v6

atw Vol. 63 (2018) | Issue 4 ı April
| | Fig. 1.
SCWL Coolant Maximum Temperature in LOFA.
| | Fig. 2.
Left: Experimental loop facility THESYS at KALLA showing location where the inter wrapper flow
experiment (see Figure 3) will be installed; right: flow diagram for the IWF tests with four parallel
channels; the valves V2.1-V2.3 control the flow through the assemblies Q1-Q3. V.2.4 controls the
flow in the gap [8].
location where the IWF experiment
will be installed is shown in Figure 2
left. Figure 2 right shows the flow
diagram of the IWF tests with four
parallel channels representing the
three assemblies (Q1-Q3) and the gap
( illustrated by the box containing
Q1-Q3). The flow and temperature
within each assembly and the gap can
be set individually by choosing valve
openings (V2.1-V2.4) and heating
rates according to the KALLA test
matrix. Figure 3 shows the geometry
of the IWF test section.
and mesh resolution for the thermoshydraulic
investigation of the gap and
the bundle. In particular, we include
the upstream components to verify
their influence on the flow field within
the test section. We employ the k-ε
turbulence model and the commercial
CFD-code Star CCM+. Our first
studied case (i) focuses on the gap
| | Fig. 3.
Geometry of the IWF test section, dimensions are in mm, the heated part
of the bundle is marked red on the left side of the figure, 600 mm, [8].
flow and our second case (ii) on the
fuel assembly. For the study of case (i)
a computational domain including
the lower flow distributer, riser pipe
( including venture tube), upper flow
vessel, and the gap are considered (for
corresponding technical drawings of
components refer to Figure 3). For the
study of case (ii) the computational
domain includes the lower flow distributer,
riser pipe (including venture
tube), one inlet expansion and a single
7-pin bundle. Flow properties of the
liquid metal Lead-Bismuth eutectic at
200 °C are employed. Note that corresponding
upstream pipes and flow
conditioners are modelled so that
all relevant geometric details are
captured. Quantifying the effect of
the flow conditioning sections is
important for future simulations, as it
would enable the use of a simpler
computational domain, which still
provides accurate results. In the future
post-test analysis, the smallest representative
computational domain (e.g.,
potentially without flow conditioner
etc.) will be used to compose a fully
coupled thermos-hydraulic simulation
of the three bundles including
the IWF in the gap. Figures 4 left
and right show the computational
domains for the pre-test studies
OPERATION AND NEW BUILD 227
2 Numerical study
A comprehensive analysis of the
experiment requires efficient simulations.
In the pre-test analysis of the
hydraulics separate simulations of the
gap region and the fuel assembly are
performed. In a first step, we determine
suitable computational domains
| | Fig. 4.
Computational domain for IWF-gap (left) and bundle (right) including the upstream domains.
Operation and New Build
Numerical Analysis of MYRRHA Inter- wrapper Flow Experiment at KALLA ı Abdalla Batta and Andreas G. Class